Motor control system



Nov. 30, 1937. N H. WILLBY m- AL MOTOR CONTROL SYSTEM Filed Feb. 5, 1937 and.

5&5

INVENTOR s. fifi'rman 191 MW? Graham L 0 WITN ESSES: 712% JM Patented Nov. 30, 1937 UNITED. STATES MOTOR CONTROL SYSTEM Norman H. Willby, Irwin,

Pittsburgh, Pa.,

and Graham L. Moses,

" assignors to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation oLP-ennsylvania Application February 5, 1937, Serial No. 124,262

10 Claims.

Our invention relates, generally, to motor control systems and, more particularly, to systems for controlling the operation of the propelling motors of electric vehicles, such as trolley coaches.

In order that maximum amount of space will be available for the passengers in a trolley coach and that good performance will be obtained without using an excessive amount of power, it is desirable that the size and the weight of the control equipment be kept at a minimum. However, the modern trolley coach must be capable of accelerating at a high rate to cope with traffic conditions and maintain fast schedule speeds, and it is necessary to provide smooth acceleration to prevent discomfort to the passengers.

An object of our invention, generally stated, is to provide a control system for an electrically propelled vehicle which shall be simple and efiicient in operation and which may be economically manufactured and installed.

A more specific object of our invention is to provide a relatively large number of accelerating steps for the propelling motor with a small amount of control equipment.

Another object of our invention is to provide an automatic accelerating system having variable rates of acceleration which may be normally varied within predetermined limits under the control of the operator.

A further object of our invention is to provide for temporarily increasing the tractive effort be yond the normal accelerating rate range to meet emergency conditions.

Other objects of our invention will be described hereinafter or will be apparent to those skilled in the art.

In accordance with one embodiment of our invention, the accelerating resistors and switches are so combined and operated that a larger number of accelerating steps or notches is obtained for the same number of switches. The accelerating switches are operated by interlock progression under the control of a current limit relay, the setting of which is normally varied by the master controller. The tractive effort may be temporarily increased. to overcome unusually heavy grades by increasing the tension on the limit relay spring by means of a pull rod provided for the operator. The accelerating switches are provided with a closing coil for operating the switch and a holding coil for retaining it in the closed position, thereby reducing the number of interlocks required and simplify the wiring of the apparatus.

For a fuller understanding of the nature and objects of our invention, reference may be had to the following detailed description, taken in conjunction with the accompanying drawing, in which:

Figure 1 is a diagrammatic view of a control system embodying our invention, and

Fig. 2 is a. chart showing the sequence of operation of a. portion of the apparatus illustrated in Fig. 1.

Referring to the drawing, the system shown therein comprises a motor I having an armature winding II and a series field winding H, a line switch LS for connecting the motor to a current collecting device l3, a resistor R which is subdivided into a plurality of sections 14 to l8, inclusive, for controlling the motor current during acceleration of the motor ill, a plurality of accelerating switches RI, R2, R3, R5, R6 and R1 for controlling the resistor connections, field shunting switches Fl, F2 and F3, a master controller MC and a limit relay LR for automatically controlling the acceleration of the motor.

The motor I may be of a type suitable for propelling an electric vehicle, for example, a trolley coach (not shown). Power for operating the motor may be supplied from any suitable source through the current collecting devices l3 and I!) which are disposed to engage overhead conductors 2| and 22, respectively.

In order to increase the smoothness of operation of the vehicle during the accelerating period, the resistor shunting switches are so disposed that they may be operated first in one sequence to shunt a portion of the resistor R from the motor circuit and then operated in a different sequence to recombine certain sections of the resistor R in the motor circuit and then shunt the resistors from the circuit step by step, thereby increasing the number of accelerating steps provided with a. certain number of accelerating switches. In this manner, a large number of accelerating steps may be obtained without materially increasing the control equipment, thereby keeping the space required for the equipment and the weight and cost of the equipment at a minimum.

With a view to further simplifying the equipment and wiring necessary for controlling the operation of the vehicle, each one of the accelerating switches is provided with a closing coil for operating the switch and a holding coil for retaining the switch in the closed position, and the sequence of operation of the switches is controlled by interlocks on the switches instead of by the usual sequence drum. Furthermore, a single interlock on each switch performs the dual function of establishing an energizing circuit for the holding coil of that switch and also the closing coil of the next successive switch, thereby materially reducing the number of interlocks required and simplifying the wiring of the equipment.

The rate of acceleration of the vehicle is controlled by the limit relay LR, which is of a high speed type having a balanced armature which permits the relay to be operated quickly enough to prevent more than one accelerating step from being taken at a time during the automatic acceleration of the vehicle. The rate of acceleration may be normally varied within predetermined limits by means of the master controller MC which is connected to the calibrating spring 23 on the limit relay by means of a chain 24, as shown. Thus, it will be seen that, as the controller drum is advanced, the tension on the spring 23 is increased, thereby increasing the current required to operate the relay and increasing the rate of acceleration of the motor II] by permitting a larger amount of current to flow through the motor between accelerating steps.

In order that the tractive efiort and thereby the rate of acceleration may be increased still further to meet emergency conditions, as, for example, when the vehicle is going up an excessive grade, a lever 25 is so disposed that the tension of the spring 23 may be increased still further independently of the position of the master controller MC. In this manner a higher value of motor current may be permitted to flow to increase the power developed by the motor. However, the lever 25 is intended for emergency use only, and is, therefore, so designed that when it is released by the operator, the normal tension as determined by the position of the controller MC, is applied to the spring 23.

With a view to increasing the maximum operating speed of the motor I0, provision is made for shunting the field winding l2 through a resistor 26 and a reactor 21. The field shunting switches FL F2 and F3 are provided for con trolling the amount of resistance in the field shunting circuit, thereby varying the field excitation of the motor I8 and controlling the maximum speed developed by the motor.

In order that the functioning of the foregoing apparatus may be-more clearly-understood, the operation of the system will now be described in more detail. Assuming that it is desired to accelerate the vehicle at the maximum rate, a switch 28 is closed to energize the control circuits and the master controller MC fully advanced, thereby closing the switches LS and Rl to supply power to the motor I8. The energizing circuit for the closing coil of the switch R| may be traced from the positive current collector I9 through a conductor 3|, the switch 28, conductor 32, contact fingers 33 and 34 bridged by contact segment 35 on the controller MC, conductor 36, an interlock 31 on the switch R6, conductors 38 and 39, the closing coil 4| of the switch RI, conductor 42, contact members 43 on the limit relay LR and conductors 44 and 45 to the negative current collector l3. The energizing circuit for the holding coil of the switch RI may be traced from the previously energized conductor 39 through an interlock 52, conductor 53, the holding coil 54 and conductors 44 and 45 to the negative current collector |3. .The energizing circuit for the actuating coil of the line switch LS extends from the conductor 36 through the coil 28 to the conductor 45 and thence to the negative current collector l3.

The closing of the switch RI establishes a motor circuit which may be traced from the positive current collector l9 through conductor 3|, the switch RI, resistors |4, l5, l6, l1 and I8 which are connected in'series circuit relation, conductor 46, the series field winding l2, conductor 41, the actuating coil 48 of the limit relay LR, conductor 49, the armature H of the motor l8, conductor 5|, the switch LS and conductor 45 to the negative current collector l3.

Since it has been assumed that the master controller MC is fully advanced, the switch R2 will be closed as soon as the motor current decreases to a value which will permit the contact members 43 of the limit relay LR to close. The energizing circuit for the closing coil of the switch R2 may be traced from the previously energized conductor 38 through an interlock 55 on the switch Rl to a conductor 56, contact fingers 51 and 58 bridged by segment 59 on the controller MC, conductor 6|, the closing coil 62 of the switch R2, conductors 63 and 42, the contact members 43 of the limit relay LR and conductors 44 and 45 to the negative current collector l3. The switch R2 is held closed by its holding coil 64 which is energized througha circuit extending from the previously energized conductor 6| through an interlock 65 on the switch R2, the holding coil 64 and conductors 44 and 45 to the negative current collector I3.

As stated hereinbefore, the interlock 65 on the switch R2 also establishes a circuit to the closing coil of the switch R3. Accordingly, this switch will be closed to further accelerate the motor as soon as the counter-electromotive force of the motor reduces its current sufilciently to permit the limit relay LR to close. The energizing circuit for the closing coil of the switch R3 may be traced from the previously energized conductor 6| through the interlock 65 on the switch R2, conductor 66, the closing coil 61, conductors 68 and 42, the contact members 43, of the limit relay LR and conductors 44 and 45, to the negative current collector l3.

Likewise, the closing of the switch R3 establishes a circuit for its holding coil and also for the closing coil of the switch R5. The holding circuit may be traced from the conductor 6| through conductor 69, an interlock II, the holding coil 12 and conductors 44 and 45 to the negative current collector l3.

The energizing circuit for the closing coil of the switch R5 extends from the interlock H in the switch R3 through conductor 13, the closing coil 14, conductor I5, an interlock 16 on the switch R3 and conductors 68 and 42 to the contact members 43 on the limit relay LR and thence through conductors 44 and 45 to the negative current collector I3. The holding coil 11 of the switch R5 is energized through a circuit which extends from the conductor 6| through conductor 18, the interlock 19, the coil 11 and conductors 44 and 45 to the negative current collector |3.

At this time, the switch R6 is closed to decrease further the resistance in the motor circuit, thereby accelerating the motor. The energizing circuit for the closing coil of the switch R6 may be traced from the previously energized conductor 36 through conductor 8|, an interlock 82 on the switch R5, conductor 83, the closing coil 84 of the switch R6, conductors 85 and 42, contact members 43 of the relay LR and conductors 44 and 45 to the negative current collector l3. The energizing circuit for the holding coil of the switch R6 extends from the conductor 8| through conductor 81, an interlock 88 on the switch R6, the holding coil 89 and conductors 8| and 45 to the negative current collector I3.

It will be noted that the closing of the switch R6 interrupts the energizing circuit for the holding coils of the switches RI, R2, R3 and R5 by opening the interlock 31 carried by the switch R6, thereby permitting these switches to be opened at this time. However, the opening of the switch R3 establishes an energizing circuit to the closing coil of the switch RI which causes this switch to be closed as soon as the contact members of the limit relay LR are closed. The energizing circuit for the closing coil of the switch R1 may be traced from the previously energized conductor 31 through the interlock 36 on the switch R6, conductor 92, the closing coil 93, conductor 94, an interlock on the switch R3, conductors 65 and 42, the contact members 43 of the relay LR and conductors 44 and 45 to the negative current collector I3. The holding coil of the switch R1 is energized through a circuit which extends from the conductor 36 through conductor- 96, an interlock 9'! on the switch RI, conductor 98, the holding coil 99 and conductors 44 and 45 to the negative current collector II.

It will be seen that the closing of the switches R6 and R1 and the opening of the switchw RI, R2. R3 and R5 connects the resistor section I6 in the motor circuit in parallel-circuit relation with the series connected resistors, I4, I 5, I6 and I1, thereby further decreasing the total resistance in the motor circuit. Following the closing of the switch R1 to establish the parallel connections just described, the switch R2 is reclosed to shunt the resistor I4 from the motor circuit. The energizing circuit for the closing coil of the switch R2 may be traced from the previously energized conductor 36 through conductor IOI, an interlock I02 on the switch R'I,

conductors I03, and 56, contact fingers 51 and 66 bridged by the segment 59, conductor 6| to the closing coil 62, conductors 63 and 42 to the contact members 43 of the limit relay LR and conductors 44 and 45 to the negative current collector I3.

The switches R3 and R5 are then operated in sequence under the control of the limit relay LR as previously described, thereby further reducing the total resistance in the motor circuit. Following the closing of the switch R5, the switch RI is again closed to shunt the remainder of the resistor R from the motor circuit and connect the motor directly to the power conductor 3|. The energizing circuit for the closing coil of the switch RI extends at this time from the con-- ductor 36 through the conductor IIII, an interlock I02 in the switch RI, conductors I03, 56 and I04, an interlock I05 on the switch R5, conductors I06, 36 and 39, the closing coil H of the switch RI, conductor 42, contact members 43 of the relay LR and conductors 44 and 45 to the negative current collector I3.

In this manner, a portion of the accelerating switches are utilized the second time during the accelerating period to shunt resistance from the motor circuit, the sequence of operation being different than it was during the first time, thereby increasing the number of accelerating steps and improving the performance of the vehicle without increasing the number of accelerating switches required.

As stated hereinbefore, the maximum speed of the vehicle is attained by utilizing the switches FI, F2 and F3 and a resistor 26 and a reactor 21 to shunt the field winding I2 of the motor I0 in successive steps. The energizing circuit for the closing coil of the switch FI extends from the previously energized conductor 36 through conductor 96, an interlock 91 on the switch R1, conductor 96, an interlock I01 on the switch Rl,conductor I08, contact fingers I09 and III bridged by the segment II2, conductor II3, the

closing coil II4 of the switch FI to the conductor I5 and thence through a. circuit previously traced to the negative current collector I3. The energizing circuit for the holding coil H5 01' the switch FI extends from the conductor I I3 through an interlock II6 on the switch FI, the holding coil II6-and conductors 44 and 45 to the negative current collector I3.

The closing of the interlock II6 on the switch FI also energizes the closing coil of switch F2 through a circuit which extends from the conductor II 3 through the interlock II6, conductor Ill and the closing coil I I8 to the conductor 15 and thence through a circuit previously traced to the negative current collector I3.

Likewise, the closing of the switch F2 establishes a circuit for its holding coil which extends from the conductor II3 through an interlock 9, a conductor I2I to the holding coil I22 and conductors 44 and 45 to the negative current collector I3. Following the closing of the switch F2, the closing coil I23 of the switch F3 is energized through a circuit which extends from the conductor II3 through the interlock II9 oi. the switch F2, conductor I24 and the coil I23 to the conductor I5 and thence through a circuit previously traced to the negative current collector I3.

As described hereinbefore, the accelerating rate of the vehicle may be varied within predetermined limits by advancing the controller MC to increase the tension of the spring 23 on the limit relay LR. Furthermore, if it is necessary to temporarily increase the tractive effort above the amount normally permitted by the limit relay LR, the lever 25 may be actuated to further increase the tension on the spring 23, thereby changing the calibration of the relay LR to permit a greater amount of current to flow through the motor I 0 before the contact members of the relay are opened to stop the progression of the accelerating switches in the manner hereinbefore described. In this manner, the vehicle is enabled to overcome unusually heavy grades or meet other unusual traffic conditions.

From the foregoing description, it is apparent that we have provided a control system which is particularly suitable for controlling the operation of trolley coaches, or similar electric vehicles, and which provides for improving the performance of the vehicle by simplifying and reducing the equipbodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all matter contained in the foregoing description and shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

We claim as our invention:

1. In a motor control system, in combination, a motor, a source of power for the motor, means for connecting the motor to the power source, a plurality of resistors for controlling the motor current, a plurality of switches for controlling the resistor connections, control means for initiating the operation of said switches, and interlocking means on said switches for causing them to be operated first in one sequence and then in another sequence to increase the number of accelerating steps.

2. In a motor control system, in combination, a motor, a source of power for the motor, means for connecting the motor to the power source, a

plurality of resistors for controlling the motor current, a plurality of switches for controlling the resistor connections, control means for initiating the operation of said switches, interlocking means on said switches for causing them to be operated first in one sequence and then in another sequence to increase the number of accelerating steps, and a current limit relay responsive to the motor current for governing the operation of said switches.

3. In a motor control system, in combination, a motor, a source of power for the motor, means for connecting the motor to the power source, a plurality of resistors for controlling the motor current, a plurality of switches for controlling the resistor connections, control means for initiating the operation of said switches, and interlocking means on said switches for causing them to be operated first in one sequence and then in another sequence to increase the number of accelerating steps, said switches having closing coils and holding coils energized through said interlocks.

4. In a motor control system, in combination, a motor, a source of power for the motor, means for connecting the motor to the power source, a plurality of resistors for controlling the motor current, a plurality of switches for controlling the resistor connections, control means for initiating the operation of said switches, and interlocking means on said switches for causing them to be operated first in one sequence and then in another sequence to increase the number of accelerating steps, each one of said switches having a closing coil and a holding coil, said closing coil being energized through an interlock on one switch and the holding coil being energized through an interlock on anothef switch.

5. In a motor control system, in combination, a motor, a source of power for the motor, means for connecting the motor to the power source, a plurality of resistors for controlling the motor current, a plurality of switches for controlling the resistor connections, control means for initiating the operation of said switches, interlocking means associated with said switches and cooperating with said control means for causing the switches to be operated first in one sequence and then in another sequence to increase the number of accelerating steps, each one of said switches having a closing coil and a holding coil, and an interlock on each switch through which the holding coil of said switch and the closing coil of the next successive switch are energized.

6. In a motor control system, in combination, a motor, a'source of power for the-motor, means for connecting the motor to the power source, a plurality of resistors for controlling the motor current, a plurality of switches for controlling the resistor connections, control means for initiating the operation of said switches, interlocking means associated with said switches and cooperating with said control means for causing the switches to be operated first in one sequence and then in another sequence to increase the number of accelerating steps, each one of said switches having a closing coil and a holding coil, an interlock on each switch through which the holding coil of said switch and the closing coil of the next successive switch are energized, and relay means responsive to the motor current and cooperating with said interlocks to control the energization of said closing coils.

'7. In a motor control system, in combination, a motor, a source of power for the motor, means for connecting the motor to the power source, a plurality of resistors for controlling the motor current, a plurality of switches for controlling the resistor connections, a controller for initiating the operation of said switches, interlocking means on said switches for causing them to be operated first in one sequence and then in a diilerent sequence to increase the number of accelerating steps, a'relay responsive to the motor current and cooperating with said interlocks to control the operation of said switches, and means actuated by said controller for governing the operation of said relay.

8. In a motor control system, in combination, a motor, a source of power for the motor, means for connecting the motor to the power source, a plurality of resistors for controlling the motor current, a plurality of switches for controlling the resistor connections, a controller for initiating the operation of said switches, interlocking means on said switches for causing them to be operated first in one sequence and then in a different sequence to increase the number of accelerating steps, a relay responsive to the motor current and cooperating with said interlocks to control the operation of said switches, spring means for governing the operation of said relay, and means for connecting said spring means to said controller for varying the tension on the spring means.

9. In a motor control system, in combination,

a motor, a source 0! power for the motor, means for connecting the motor to the power source, a plurality of resistors for controlling the resistor connections,- c. controller for initiating the operation of said switches, interlocking means on said switches for causing them to be operated first in one sequence and then in a different sequence to increase the number of accelerating steps, a relay responsive to the motor current and cooperating with said interlocks to control the operation of said switches, spring means for governing the operation of said relay, means for connecting said spring means to said controller for varying the tension on the spring means, and additional means for varying the tension on said spring means independently of the controller.

10. In a motor control system, in combination, a motor, a source of power for the motor, means for connecting the motor to the power source, a plurality of resistors for controlling the motor current, a plurality of switches for controlling the resistor connections, a controller for initiating the operation of said switches, interlocking means on said switches for causing them to be operated first in one sequence and then in a different sequence to increase the number of accelerating steps, a relay responsive to the motor current and cooperating with'said interlocks to control the operation of said switches, spring means for governing the operation of said relay, means for connecting said spring means to said controller for normally varying the tension on the spring means within predetermined limits, and additional means for increasing the tension on said spring means independently of the controller.

NORMAN H. WILLBY. GRAHAM L. MOSES. 

